Current ophthalmic diagnostic and measurement systems typically use wavefront acquisition and diagnostic capabilities to deliver measurement accuracy, thereby enhancing the precision of laser vision correction surgery. An exemplary ophthalmic diagnostic and measurement product using wavefront is the Abbott WaveScan WaveFront System, which, among having other capabilities and technologies, uses a Shack-Hartmann wavefront sensor that can quantify aberrations throughout the entire optical system of the patient's eye, including second-order aberrations related to spherical error and cylindrical errors, and higher-order aberrations related to coma, trefoil, and spherical aberrations. An exemplary wavefront diagnostic system was described in U.S. Pat. No. 7,931,371 to Dai, and is herein incorporated by reference in its entirety.
In addition to its use in ophthalmic diagnostic and measurement systems, laser technology has become the technique of choice for ophthalmic surgical applications, such as refractive surgery for correcting myopia, hyperopia, astigmatism, and so on, as well as procedures for treating and removing a cataractous lens. Known laser-assisted ophthalmic surgical systems typically use a variety of forms of lasers and/or laser energy to effect vision correction, including infrared lasers, ultraviolet lasers, picosecond lasers, femtosecond lasers, wavelength multiplied solid-state lasers, and the like. Laser-assisted ophthalmic surgical systems often also use wavefront diagnostic systems to accurately measure the refractive characteristics of a particular patient's eye.
A wavefront diagnostic system generally captures eye images during wavefront measurement. A pupil camera in an aberrometer captures images of the eye, illuminated by infrared light-emitting diodes (LEDs) designed as a symmetric configuration. These eye images are used, for example, for iris registration for laser vision correction. Eye images from the diagnostic system, however, often show the sclera on the nasal side as appearing brighter than the sclera on the temporal side. This is true for both the right eye and the left eye. The eye image is essential for wavefront-guided corneal refractive surgery since it identifies the treatment area and is used for eye tracking. The pupil itself is not a reliable marker for the treatment area because its size and center change depending on the lighting condition or administered medication. The outer iris boundary (OIB), a circular boundary between the iris and the sclera of the eye, however, is fixed. The aberrometer thus identifies this boundary from the eye image for the iris registration for laser vision correction. But, most eye images captured by the pupil camera show that the sclera on the nasal side looks brighter than the sclera on the temporal side, both from the right eye (OD) and the left eye (OS). This imbalance illumination is typically caused by secondary reflections of infrared LEDs by the patient's nose. FIG. 1 shows typical eye images, captured during wavefront measurement where the pupil illumination uses infrared LEDs. The image shows the sclera on the nasal side appearing brighter than the sclera on the temporal side for both the right eye (OD) and the left eye (OS). The imbalance illumination can cause failure in detecting the OIB, and as such, it is desirable to correct it in the diagnostic system for laser-assisted ophthalmic surgery.
Accordingly, improved systems and methods for balancing infrared illuminations in eye imaging are desirable.